In a primary system of a pressurized water reactor-type nuclear power plant (hereinafter referred to as PWR) and a primary system of a boiling water reactor-type nuclear power plant (hereinafter referred to as BWR), which have been operated for an extended period of time, radioactive CRUD may be deposited, and radioactive nuclide may be incorporated into an oxide film on a surface of primary system piping and instrument. The radioactive CRUD and the radioactive nuclide incorporated into the oxide film are radiation sources and cause exposure to radiation. For this reason, it is preferable that the radioactive CRUD and the radioactive nuclide incorporated into the oxide film be removed as much as possible.
Since the 1980s, the radiation dose of a nuclear power plant has tended to reduce smoothly. However, in recent years, a reduction in the radiation dose has been stopped. Therefore, in addition to conventional dose reduction measures, additional measure has been desired.
To a primary system of a conventional nuclear power plant, zinc injection has been applied for a reduction in radiation exposure. The application of zinc injection takes a certain effect for a reduction in the dose rate of primary system instrument and piping (for example, see Patent Literature 1).